This invention pertains to apparatus for tuning the notes of a musical instrument. More particularly, it pertains to such apparatus which is of the type that employs a rotary strobe wheel.
It is common practice today in the tuning of a musical instrument, such as a piano or harpsichord, to use a strobe-wheel-type tuning device wherein a rotary strobe wheel is turned in front of a flashing lamp, the flashes of which occur at the frequency of the particular note in the instrument which is being tuned at a given time. In such a device, the particular speed at which the strobe wheel turns is a matter of adjustment--this speed being adjusted each time that a different note in the usual scale of notes is to be tuned. It is obviously important that in such a device the selected rotational speed of the strobe wheel be accurately and easily adjustable. To this end, it is desirable to maintain the overall construction of such a tuning device as simple as possible so as to minimize the likelihood of inaccuracy.
A general object of the present invention is to provide a unique strobe-wheel-type tuning device wherein the above considerations are taken into account in a very practical and satisfactory manner.
More particularly, an object of the invention is to provide such a tuning device wherein extremely accurate control is provided for controlling the speed of a rotary strobe wheel.
Another object of the invention is to provide a device of the type generally indicated which is characterized by extremely simple construction.
Still a further object of the invention, and one that is directly related to the immediately preceding object, is to provide a tuning device which is of relatively low cost construction despite its high degree of accuracy.
According to a preferred embodiment of the invention, apparatus is provided for turning a conventional strobe wheel--this apparatus featuring side-by-side rotary shafts including a driving shaft and a driven shaft--the former having a uniform outside diameter, and the latter having a taper which is based on the mathematical formula that determines the usual intervals between successive notes in most conventional musical instruments. The driving shaft is turned at a selected sustantially constant speed. The driven shaft is turned through an endless elastic band which couples the two shafts. The latter-mentioned shaft is directly coupled to a strobe wheel.
As is widely recognized by musicians, and by people who tune musical instruments, it is now substantially universally accepted that the thirteen sounds of a musical Octave are distributed, frequency-wise, in accordance with what is known as the Equal Tempered Scale, wherein between the 13 separate sounds there are twelve successive equal semitones. The frequency ratio of the equalized semitones is the twelfth root of the Octave ratio 1:2, or 1:1.0594631. The number 1.0594631 will be referred to also herein by the letter b. In other words, there is a definite mathematical formula, based on this division of the Octave into twelve semitones, which can be used to express the frequencies of successive notes in the different octaves. This formula is as follows: EQU F.sub.n =F.sub.O .times. b.sup.n
where:
F.sub.n is the desired frequency of the nth note above the lowest note of the instrument, F.sub.O is the frequency of the lowest note in the instrument, and n is the number of the desired note above the lowest note in the instrument.
The taper of the driven shaft mentioned above is derived herein, as will shortly be explained, in accordance with the above mathematical formula.
Various other objects and advantages and features which are attained and offered by the present invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.